mm/huge_memory: avoid reinvoking folio_test_anon()

mm/huge_memory: avoid reinvoking folio_test_anon()

Patch series "mm/huge_memory: cleanup __split_unmapped_folio()", v3.

This patch series cleans up and optimizes the internal logic of the
__split_unmapped_folio() function.

The goal is to improve clarity and efficiency by eliminating redundant
checks, caching stable attribute values, and simplifying the iteration
logic used for updating folio statistics.

These changes make the code easier to follow and maintain.

The split_huge_page_test selftest pass.

This patch (of 4):

During the execution of __split_unmapped_folio(), the folio's anon/!anon
attribute is invariant (not expected to change).

Therefore, it is safe and more efficient to retrieve this attribute once
at the start and reuse it throughout the function.

Link: https://lkml.kernel.org/r/20251021212142.25766-1-richard.weiyang@gmail.com
Link: https://lkml.kernel.org/r/20251016004613.514-1-richard.weiyang@gmail.com
Link: https://lkml.kernel.org/r/20251016004613.514-2-richard.weiyang@gmail.com
Link: https://lkml.kernel.org/r/20251021212142.25766-2-richard.weiyang@gmail.com
Signed-off-by: Wei Yang <richard.weiyang@gmail.com>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: wang lian <lianux.mm@gmail.com>
Reviewed-by: Barry Song <baohua@kernel.org>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Mariano Pache <npache@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Nico Pache <npache@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>